Kindle 3 powers this diy LED light

ePaper displays are easy on the eyes because there’s no flickering backlight to put strain on them. This is great until you’re trying to read in a dim environment. Of course Amazon will sell you a backlight that’s powered from the reader itself if you’re willing to pay. [Txoof] thought the price was a bit too high so he built his own version.

There are two pockets in the top of the Kindle reader for hooks to grab onto. Each has an electrical contact in it and together they provide about 4V of power. To patch into that source [Txoof] cut his own hooks from brass stock and mounted them onto a piece of basswood. He then cut and bent a hood from more of the brass stock to house the LEDs. A series of three of the white diodes draw their power from the hooks and shine onto to the display. As you can see this works just fine, but could benefit from just the right diffuser.

Fabric speaker

The theory behind speaker operation is pretty simple. There’s a coil that is attached to some type of diaphragm and a permanent magnet. When electrical signals pass through the coil a magnetic field is generated, and that field’s interaction with the permanent magnet causes the diaphragm to vibrate and create sound. But we’ve always assumed that the vibrating material must be stretched tight for this to work. [Hannah Perner-Wilson] proved us wrong by making this speaker out of fabric. It uses conductive tape as the coil on a heavy piece of canvas. The permanent magnet is resting on a table and for the demonstration the fabric is just laid on top.

Check out the video after the break to hear the sounds generated by this device as well as a design that uses conductive thread instead of tape. This gets us wondering if what we’re hearing is the result of the magnet vibrating against the tabletop? Let us know your thoughts, and if you’ve got any information about the paper-backed circuit (seen at 0:04 into the video) driving the speakers we’d love to hear about that too.

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Easy to build rig prevents reflow soldering mishaps

reflow_soldering_rig

[Erich aka VK5HSE] performs quite a bit of solder reflow work, but has always been concerned about bumping his circuit boards once the solder has liquified and is ready to be removed from the heat source. He says that removing workpieces from toaster ovens often results in the unintentional jarring of a circuit board full of components sitting on molten solder, and he wanted to find a solution.

Using some off-the shelf components from a local hardware store, he built a rig that fits on top of a hot plate, allowing him to move hot circuit boards away from the heat source in a smooth controlled motion. The rig is pretty simple, not only preventing unwanted workpiece movement, but also making it easy to regulate the amount of time a circuit board is allowed to heat.

He suggests that his design is not absolutely ideal, and that it can easily be improved upon in several ways without adding significant cost to the project.

Repair parts from unlikely sources

baby_swing_motor_replacement

[Jay] sent us some details of a quick fix for a baby swing he owns, along with the unlikely place where he found replacement parts. We showed you a pair of his creations earlier this week, which you might recall. As luck would have it, the motor on the baby swing he modified burned out shortly after we featured his hack. Don’t worry – he didn’t break the swing when he hacked it, nor is there a Hack-a-Day curse. It’s purely coincidence, we swear!

The swing is about 7 years old so the burned out motor wasn’t that huge a surprise. After doing some research, it was looking like he would likely need to shell out $70-$100 for a replacement motor. He luckily stumbled upon a forum thread that said a motor from a cheap air freshener was a perfect match, so he gave it a shot.  Sure enough, it was the same motor, but with more torque. All it took was $5 to get the swing up and running good as new.

It just goes to show that you never know useful common items can be until you take them apart to see what’s inside.

Remote phone control using Bluetooth and a video stream

remote_bluetooth_phone_control

Hack-a-Day reader [Bobbie] sent us a hack that is an adaptation of the automatic cell phone button pushing machine we featured earlier this week. Inspired by that project, he challenged himself to construct a more efficient way to tackle the problem.

He started out in much the same fashion, pointing a camera at the phone in order to view the display remotely. The main thing he focused on to make his project unique was they way in which the buttons on the phone were activated. He was impressed by the mechanical button pressing rig, but thought it to be overly complicated. Instead, he decided to send button presses over Bluetooth to his phone which happened to be AT+CKPD compatible (PDF).

Not only that, his interface is quite impressive too. Originally planning to use the keyboard to send input to the phone, he changed course and programmed his video stream GUI to register mouse clicks instead. Now, when he clicks one of the phone’s buttons in the video display, the appropriate button press is sent to the phone – Awesome!

Keep reading to see a video of his remote phone interface, you’ll be glad you did.

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AM/FM SOS beacon saves your bacon

bacon_beacon_breadboard

[BadWolf] sent us a device called the “Bacon Beacon“, which is his 555 Design Contest entry. In short, it’s a life-saving device that emits an S.O.S. signal in Morse code over both the AM and FM bands. The device uses five 555 timers to get the job done, each of them dedicated to a specific task. Three of the timers are used for clocking and Morse generation, while the remaining two are used to produce and transmit an audible signal over the air waves. Currently, the signal can be received about a mile away from the source, which would theoretically allow for a search and rescue team to locate you with a simple radio and directional antenna.

The current design is still a bit rough around the edges, but the final plans would have the circuit built into a flashlight-like device equipped with red and green signaling LEDs. It’s a clever project and would make for a great tool if you got lost while hiking, or in the event of a zombie apocalypse.

Stick around for a quick video of the Bacon Beacon in action, and swing by [BadWolf’s] site if you want to know why his project has such a strange moniker (hint: it’s not because it can “save your bacon”).

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Google two-factor authentication in a wristwatch

chronos_two_factor_authentication

The Chronos watch from Texas Instruments is a handy little piece of hardware if placed in the right hands. If you are not familiar with the platform, it is marketed as a “wearable wireless development system that comes in a sports watch”. In plain English, it’s a wearable wireless MCU mated with a 96 segment LCD, that boasts an integrated pressure sensor and 3-axis accelerometer. It is capable of running custom firmware, which allows it to do just about anything you would like.

[Huan Trong] wanted to take advantage of Google’s new two-factor authentication, and decided his Chronos would make a great fob, since he would likely be wearing the watch most of the time anyhow. He put together some custom firmware that allows the watch to function as an authentication fob, providing the user with a valid Google passcode on command.

He does warn that the software is alpha code at best, stating that it doesn’t even allow the watch to keep time at the moment. We are definitely looking forward to seeing more code in the near future, keep up the great work!

Be sure to stick around to see a video of his watch in action.

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